A One-Pot Ultrasound-Assisted Almond Skin Separation/Polyphenols Extraction and its Effects on Structure, Polyphenols, Lipids, and Proteins Quality

Malak Tabib,Njara Rakotomanomana,Yang Tao,Adnane Remmal,Farid Chemat,Christian Ginies,Isabelle Bornard

doi:10.3390/app10103628

Abstract

Almond skin is an important by-product in the almond processing industry, rich in potentially health-promoting phenolic compounds. The objective of this present study is to separate the skin from the almond and extract its polyphenol contents using Ultrasound-Assisted Extraction (UAE) at room temperature. Optimization was performed according to a two-variable central composite design (CCD), and the optimum combination of ultrasonic intensity and extraction temperature was obtained through multi-response optimization: ultrasonic intensity (UI), 9.47 W.cm−2; and temperature, 20 °C for an extraction time of 20 min. Under the above-mentioned conditions, total phenolic content was 258% higher with UAE than silent experiment. Mathematic modelling and microscopic investigations were achieved to enable understanding physical and structural effects of ultrasound on almond skins and comprehension of the mechanism behind the enhancement of mass transfer phenomena. Scanning Electron Microscopy (SEM) showed different acoustic cavitation impacts including fragmentation, sonoporation, and erosion. Extracts were analyzed by ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS), identifying a combination of flavanols, flavanones and non-flavonoids. UAE shows no negative effect on almond proteins and lipids when compared to natural almonds (NS).

Highlights

Almond (Prunusdulcis, dulcis,RosaceaeRosaceaefamily) family) is is one one of of the the most (Prunus most consumed consumeddrupes drupesininthe theworld, world, appreciated for its pleasant taste and its abundance in nutritional compounds (proteins, polyphenols, appreciated for its pleasant taste and its abundance in nutritional compounds,9), and known [1,2]
Ultrasonic power and temperature are the variables involved in the Central Composite Design (CCD) that could potentially affect polyphenol extraction efficiency in order to evaluate and optimize ultrasound extraction of polyphenols (TPC) and almond skin separation time (SST)
According to CCD experiments provided by STATGRAPHICS, experiments were performed at maximum ultrasonic intensity (UI) 9.47 W.cm−2 to fit the limits of the ultrasonic device, and at temperatures between 18 ◦ C and 61 ◦ C

Summary

Introduction

Almond (Prunusdulcis, dulcis,RosaceaeRosaceaefamily) family) is is one one of of the the most (Prunus most consumed consumeddrupes drupesininthe theworld, world, appreciated for its pleasant taste and its abundance in nutritional compounds (proteins, polyphenols, appreciated for its pleasant taste and its abundance in nutritional compounds (proteins, polyphenols, omega6, omega and knownfor foritsitshypercholesterolemia hypercholesterolemia reduction reduction [1,2]. omega 6, omega9),9), and known [1,2]. Rosaceaefamily) family) is is one one of of the the most 6, omega and knownfor foritsitshypercholesterolemia hypercholesterolemia reduction reduction [1,2]. 9),9), and known [1,2]. Especially California, dominates the global production of almonds, followed by the America, especially California, dominates the global production of almonds, followed by the European.

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Conclusion